This invention relates to manufacturing technology, and, more particularly, to the manufacturing of articles of composite materials.
Organic-matrix composite materials are used in structures because of their excellent mechanical properties, low weight, and ability to tailor the properties of structures made of these materials to meet specific needs. The composite materials have reinforcing fibers such as carbon fibers embedded in an organic matrix material such as a curable epoxy resin. The use of the composite materials has required the development of new manufacturing technologies, because the composite materials are furnished in a precursor form. One form of precursor is fiber bundles which are positioned to the desired shape and then enrobed in the flowable matrix precursor composition, which is later cured to a hardened state. Another form of composite material precursor is prepreg plies constituting fibers embedded in a partially cured resin material, which are collated (laid up) onto a form into the desired shape and later fully cured.
In one conventional manufacturing approach using prepreg precursor material, the individual plies of the prepreg are collated onto a tool, and a matching tool is pressed against the exposed side of the collated prepreg, while the assembly is heated. The combined heating and pressing consolidates the prepreg material and thereafter causes it to cure and harden. The matching tool may be either a rigid tool or a sheet of rubber bladder material against which a gas pressure is applied. Rigid matching tools are relatively expensive to make and use. Rubber bladder matching tools are limited as to the type of structures that may be produced.
In either case, gas released from the composite material during compacting must be removed, and excess resin material that is extruded out of the composite material as it compacts must be conducted away from the composite material. To accomplish these functions, a breather cloth is typically placed against the surface of the collated composite material. The breather cloth provides a pathway for removal of the evolved gas and, to a minor extent, the excess extruded resin. Bleeder openings may also be provided through the tooling to remove resin in amounts greater than may be accommodated by the breather cloth. The presence of a large amount of excess resin to be removed may preclude the use of a rubber bladder as a pressure tool.
The inventor has recognized a need for an improved technique for manufacturing composite articles that is relatively inexpensive and allows the processing of precursor materials having large amounts of evolved gas and extruded resin. The present invention satisfies this need, and further provides related advantages.